/Engine/Plugins/Experimental/GeometryScripting/Source/GeometryScriptingCore/Public/GeometryScript/MeshMaterialFunctions.h
Assigns the specified triangle the given Material ID. If the Target Mesh does not have Material IDs enabled, or if the Triangle ID is not an element of the Target Mesh then bIsValidTriangle will be set to false.
static [UDynamicMesh](API\Runtime\GeometryFramework\UDynamicMesh) * SetTriangleMaterialID ( [UDynamicMesh](API\Runtime\GeometryFramework\UDynamicMesh) * TargetMesh, int TriangleID, int MaterialID, bool & bIsValidTriangle, bool bDeferChangeNotifications )